496 Proceedings of the Royal Society 
traverses across the largest and most important islands, and touched 
here and there at several of the smaller ones. They have constructed 
a geological map of the group, upon which is shown the outcrop of 
the coal-seams of Suderoe, the direction of numerous dykes of basalt, 
the position of great intrusive sheets of the same rock ; and the 
trend of the glaciation is indicated by arrows. The introductory 
part of this paper gives some account of the geological observations 
made by previous writers — Jorgen Landt in 1800, Mackenzie and 
Allan in 1815, Trevelyan a year or two later, Forchhammer in 1824, 
Eobert Chambers in 1854, and Johnstrup in 1873. The general 
physical features of the islands are next described, the extent of land 
being roughly estimated at about 600 square miles. Nearly all the 
islands have an elongated form, and are drawn out in aN.N.W. and 
S.S.E. direction. This is likewise the direction of the more or less 
narrow sounds or open fiords that separate the islands in the northern 
part of the archipelago, as also of the wider belts of water in the 
south. All the islands have a mountainous character, and everywhere 
exhibit, in the most marked manner, the well-known terraced outline 
which is so common a feature of trappean masses, the highest eleva- 
tion they attain is 2852 feet, but many of the hills approach to 
within 200 or 300 feet of that dominating point. The mean eleva- 
tion of the northern group of islands is estimated to exceed 800 
feet, and is probably not less than 900 feet. The coasts are usually 
precipitous, many of the cliffs exceeding 1000 feet, and in some 
places even 2000 feet in height. The valleys are described as 
ascending from the sea in a series of great steps or terraces — each 
terrace being cirque-shaped and framed in by a wall of rock, the 
upper surface of which stretches back to form the next cirque-like 
terrace, and so on in succession until the series abruptly terminates 
at the base, it may be, of some precipitous mountain. Occasionally 
the col between two valleys is so level that it is difficult to detect 
the actual water-parting. In this case the two valleys combine to 
form a kind of deep hollow passing right across the island from sea 
to sea. Lakes are very numerous, but of small size, and the streams 
are also abundant but of inconsiderable importance. 
The author then goes on to describe the geological structure of the 
islands, which is extremely simple. The rocks consist principally 
of bedded basalts with intervening layers of tuff, and in Mygenses 
